It is a notebook in which the students of a particular class or group (normally at high school) write their innermost feelings and thoughts in turn when they are going to leave school and start a new life. The process of writing is initiated by a particular student. The notebook, then, is passed from one student to another until it returns to the initiator who will keep it as a memento of his/her schooldays.
What is it in E, please?
(Is it all right to be an AUTOGRAPH NOTEBOOK?)
In BE, we call them autograph albums.